hello,thank you for your answers. Well i didnt think about the memory yet.Is it possible to use an sd card or external memory on dip chips?? even if the sd card is slow in reading and writing i have the buffer of the internal memory ...

edit : i just looked in the datasheet of the at90usb162 from atmel. it has 16kb internal flash memory.

if I just handle 8 bit data with a sample speed of 48kHz this menas i would have 16/48 (about 330ms) seconds sampletime if i think the right way.thats something to start with i think.

Well, for starters , the flash memory is program memory, and is only writable from the boot area (assuming the device supports self-programming), and secondly, it's only normally rated for 10 000 erase/write cycles.